Osiris: Building Hierarchical Representations for Agricultural Environments

3D scene graphs have recently emerged as a powerful and human-understandable way of representing com- plex 3D environments. These describe environments through a layered or hierarchical graph where nodes represent different spatial concepts (from low-level geometry to higher-level scene- scale reasoning) and the edges between them represent relation- ships. While these representations have shown great promise in indoor well-structured environments, their use in outdoor structured environments such as agricultural environments has been under-explored. A key challenge here is that concepts and structures often observed in urban indoor environments cannot be easily transferred to these novel scenes. Motivated by this challenge, this paper presents Osiris which is a 3D scene graph builder for agricultural environments. We first propose a structure of the hierarchical graph for agri- cultural environments consisting of rowed crops and through our proposed system Osiris incrementally construct a 3D scene graph of agricultural environments from data taken onboard a mobile robot. We validate and evaluate the performance of Osiris using real-world data collected at several farms and show that this system is able to accurately get to the underlying structure of these agricultural environments while presenting a metrically accurate and human-understandable representation.